Integrated circuits and optoelectronic devices are becoming increasingly complex. This complexity is generally accompanied by a reduction in device dimensions and increased packing density. High processing temperatures, which were once tolerable in larger devices, are becoming unacceptable. Advances in deposition technology for depositing the various layers which may be used in such devices at decreased processing temperatures while maintaining film quality are required.
Generally, one reaches a point when reducing the temperature of a substrate during deposition of a film that will result in reduced quality of the deposited film unless nonthermal energy is added to the reacting system. Oxides such as aluminum oxide and silicon oxide as well as tantalum oxide have been the subject of study for many years and a variety of deposition techniques have been reported, including, chemical vapor deposition (CVD), plasma enhanced CVD, reactive sputtering, evaporation, RF sputtering, photochemical deposition and plasma deposition. Thermal CVD films have been produced using a variety of chemistries including the reaction of an oxidant, e.g., oxygen or nitrous oxide, with a metallo-organic compound or a metallo-chloride as the metal source. For example, in the case of aluminum oxide deposition, oxygen or nitrous oxide has been used in combination with trimethylaluminum or aluminum trichloride. Also, thermal decomposition of metal alkoxides such as aluminum tri-isopropoxide has also been employed. We have now discovered a modified plasma enhanced deposition technique which allows for the deposition of aluminum oxide films of high quality, at temperatures lower than heretofore achieved. This is particularly important in semiconductor applications, wherein the semiconductor device already possesses an aluminum film thereon or a film of another relative low melting material, where it is necessary that any subsequent film to be deposited or grown thereover be deposited or grown at temperatures less than the temperature that would cause melting or any other detrimental effect to the previously deposited film.